At this state of technology, several types of cochlear implants are known. These implants are conceived to improve the hearing of patients whose cochlea is not able to transform acoustic signals in nerve impulses.
Basically, a cochlear implant is a transducer that transforms acoustic signals in electric signals, applied to the hearing neural tissue by means of electrodes.
Cochlear implants usually include a round-shaped electrode carrier guide, with a series of electrodes lined up along it. The carrier guide is implanted in the scala tympani so that electrodes may remain close to the modiolus of the cochlea.
Patients treated with cochlear implants have extensively benefited from them. However, the conventional electrode carrier guides described above present some limitations.
First of all, its intracochlear insertion may result into damage the cochlea, by jeopardizing its anatomy and its function. We must not forget that the patients needing these systems are, for example, 2-year-old kids, with a life expectancy of 100 years, so the use of an atraumatic system is needed. Therefore, the potential use of other therapeutic treatments is not limited, and it enables to preserve residual hearing. This would permit to extend the indication of implants to people with a sensorineural hearing loss less severe than currently.
Another limitation to the traditional electrode carrier guides is that they only host up to 22 active electrodes, which limits the possibility to reproduce a more acute, punctual and versatile stimulation of the hearing neural tissue.
Besides, conventional carrier guides are hand-made by highly qualified and experimented staff. For obvious reasons, the production system is slow and expensive, plus it is highly probable that the resulting carrier guides contain a relatively high number of failures.
It has been recently proposed—for example in the patent application WO 02/080817—a cochlear implant with a flat electrode carrier guide, meant to be implanted externally to the scala tympani, exactly between the spiral ligament and the endosteum.
An implant such as the one described in this document has an advantageous feature regarding the traditional intraluminar implants: it may be inserted without damaging the morphology and function of the hearing neural tissue. However, even though this document recommends a maximum size for the electrode carrier guide, it does not suggest that the carrier guide may have a different structure from the one that conventional carrier guides have, or that it may not be automatically produced.